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18 lb Brisket at 225°F

Wrapped in butcher paper, a 18 lb whole packer at 225°F runs about 25 h 5 m of cook time — plan 27 h 5 m door to table with a 2-hour rest. For dinner at 5 PM, put it on at 1:45 PM the day before. Adjust anything below and the plan recalculates.

Brisket Cook Time Calculator

Put it on at

1:45 PMthe day before

Total time
27 h 5 m (25 h 5 m cook + 2 h rest)
Realistic range
24 h 5 m – 30 h 5 m
Pit temperature
Wrap
Cut
Rest / hold (hours)

Your timeline

  1. 1:45 PMBrisket on the smoker · the day before
  2. 1:03 AMStall begins (~150–170°F internal)
  3. 3:34 AMWrap it
  4. 12:21 PMStart probing for tenderness
  5. 2:52 PMPull it (~203°F, probe-tender)
  6. 5:00 PMSlice and serve

Planning estimates at ±12% — thickness matters more than weight, and no two briskets cook alike. The clock never decides when it's done: brisket is done when a probe slides into the thickest part of the flat like warm butter, around 203°F internal. Cook to feel, serve on time by resting longer — a wrapped brisket holds beautifully for hours.

When to start a 18 lb brisket at 225°F

Butcher paper wrap, whole packer, 2-hour rest. Start times round down to the quarter hour — early is free, late is dinner at nine.

Serving atPut it on at
12:00 PM lunch8:45 AM · the day before
3:00 PM11:45 AM · the day before
5:00 PM1:45 PM · the day before
7:00 PM3:45 PM · the day before

Wrapped or naked at 225°F?

Wrapping shortens the stall. Foil is fastest but softens bark; butcher paper is the standard compromise; no wrap costs time and buys crust.

WrapCook timeWith 2 h rest
Butcher paper~25 h 5 m~27 h 5 m
Foil (Texas crutch)~22 h 55 m~24 h 55 m
No wrap~27 h~29 h

Cooking a flat instead of a whole packer? A trimmed flat is thinner and finishes faster — figure about 22 h 35 m at 225°F in paper.

225°F: the overnight classic

225°F is the traditional low-and-slow temperature, and at 1.5 hours per pound it is the slowest road there is: a 18 lb packer wants about 25 h 5 m wrapped in butcher paper, and 27 h if you run it naked for maximum bark. That length is not a bug — it is why 225°F cooks are usually overnight cooks. You put the brisket on the evening before, sleep through the boring middle hours, and wake up around the stall.

The payoff for the patience is forgiveness. At 225°F everything happens slowly, including your mistakes: a temperature swing or a long fuel change costs you minutes, not dinner. If this is your first brisket, this temperature and a 18 lb packer is a very defensible plan.

A 18 lb packer is a big brisket. Thickness, not weight, is what really sets cook time, and big packers are thick — hold the estimate loosely, expect the stall to drag, and lean on the built-in hold if it finishes early.

How many people does a 18 lb brisket feed?

Trimming and a long cook take roughly half the raw weight, so a 18 lb packer yields about 9 lbs of sliced brisket. Plated at half a pound per adult, that is 18 people; chopped into sandwiches at a third of a pound, closer to 27 servings. Feeding a crowd near 20? The brisket for 20 people page does the shopping math, and the portion calculator handles kids, sides, and leftovers.

Quick answers

How long does a 18 lb brisket take at 225°F?

About 25 h 5 m wrapped in butcher paper, or 27 h unwrapped — plan 27 h 5 m total with a 2-hour rest. The honest range is 24 h 5 m to 30 h 5 m, because thickness matters more than weight and no two briskets cook alike.

When should I start a 18 lb brisket at 225°F for dinner at 5 PM?

Put it on at 1:45 PM the day before. That includes the cook plus a 2-hour rest, and the start time is rounded down to the quarter hour — starting early is free, because a wrapped brisket holds for hours.

How many people will a 18 lb brisket feed?

A 18 lb raw packer yields roughly 9 lbs of sliced brisket after trimming and cooking — about 18 adults as a plated main at half a pound each, or around 27 sandwiches at a third of a pound each.

Other briskets at 225°F